Bluffing, gambling, negotiation, backstabbing, outrageous reversals—this game has it all. And a thick, gooey science fiction theme to boot! The rules are simple, almost laughably so, but that's not where the game is. The game is in finding the most clever way in which to use those rules to your advantage, no matter how bleak the situation. Taken at face value, it's pretty lame, and I can see why some people hate it so. Add in a bunch of raucous, cunning friends and the game surprises and delights every time. I'm constantly surprised at some of the subtle ways "I'm screwed" moments can turn into a big win.
Negotiated (or even forced) multi-wins are great since they keep the playing time more than tolerable (read: occasionally too short—but what the hell, let's play again!).
Cosmic Encounter is the greatest game ever made. So much variety, and a rules framework that knows when to get out of the way and encourage above the table treachery. It's also one of those "the more, the merrier" games. I don't even want to play this game with less than 4 people.
If you like a heavy dose of negotiation, backstabbing, unique player powers, and card play, you can't do better. There's a reason that this game is still in the conversation after literal decades.